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Old 02-05-2021, 07:45   #1
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Wiring both parallel and linear in one array...can I do so?

We are adding five more 100w panels to a six-100w panel array that is wired linearly. Some articles suggest that additional panels (wired parallel) can increase the amps without increasing volts by adding additional panels in parallel to our existing system. MTTP we use is a Victron. Batteries are four-100w Battleborn LifePo4 wired in parallel (may add two more w more solar)

Specifically my questions are:
1. Can I use one MTTP and just connect all panels (some parallel some linear) to the single unit?

2. Our run from solar to MTTP is about 20-23 feet and so I assume the linear wiring (was done by a licensed boat electrician at a Hinckley yard before we purchased her) was done because he wanted to avoid power loss in the run from the array to the MTTP. But our catamaran mast and boom cast occasional shadow and I understand that IF partial shade, then parallel is better. Why not some of both and link it all up in one MTTP? How much of each (??) and would this be safe/efficient to connect
An array with partial linear and partial parallel?

If OK,I suppose I can later play with the array to maximize the output between the volts and amps. Within specs for MTTP of course

Please advise before I screw something up. Local installers not interested in project - job too little and they are too busy.

Thanks in advance for any helpful comments!
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Old 02-05-2021, 09:53   #2
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Re: Wiring both parallel and linear in one array...can I do so?

If you wire them to increase the voltage you will need smaller wiring. And with an mppt you will have charge voltage even in low-light situations. With that many panels you're probably better to wire some in series and some in parallel. I think the best is to have multiple controllers. That way if some panels are shaded or not charging they're not dragging down the rest
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Old 02-05-2021, 11:00   #3
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Re: Wiring both parallel and linear in one array...can I do so?

Lots to consider, and it really depends on where the panels are mounted and what kind of sun they get.

For panels in series, you will get better efficiency and they will work better in low light. The tradeoff is that if one panel is shaded (or even just part of a panel) the output of all panels in the series is pulled down. Shading half a panel could kill almost all the output of every panel of the array. So it's best to only use Series if all of the panels will get sunlight without shading.

Parallel Panels can tolerate a single panel being shaded, but are less efficient, require more light to start working, and produce higher currents and require heavier wire.

"Best" is a separate controller for each panel, but who wants 11 controllers on their boat? So, we compromise. On my boat, I have 2 100W panels on each side. Because the panels on one side will be subject to the same lighting, they are in series. Then the 2 sides are paralleled together. I then have 3 more panels that are in more random places that are paralleled together on a second controller.

As you are planning, consider balance. The wattage and voltage of any panels in parallel needs to be the same, or as close as you can get it. You don't want to parallel a 40V 200W panel with a 20V 100W panel. You most certainly don't want to parallel a few 100W panels with 6 100W panels that are in series. But you could to 5 in series paralleled with 5 more in series, provided the voltage of the panels were all the same.
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Old 02-05-2021, 11:30   #4
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Re: Wiring both parallel and linear in one array...can I do so?

When panels are wired in series (“linear”) they are referred to as a string. When you wire panels or strings in parallel they should have the same Voc and Vmp (voltage - open circuit and voltage - maximum power). Your MPPT controller gets maximum power by choosing a voltage at which to run the panels/strings. If the Vmp for the strings is different then the MPPT will choose the “wrong” voltage for at least one set of panels and you won’t be getting maximum power.

You say you have 6 panels in the current string and are proposing 5 panels in the new string. Assuming all the panels are the same Voc/Vmp, if you wire to the same controller the controller will treat each string as if it has 5 panels and you will lose one panel’s worth of production.
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Old 03-05-2021, 09:04   #5
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Re: Wiring both parallel and linear in one array...can I do so?

In basic electricity, electrical circuits are either PARALLEL or SERIES or combinations or both.
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Old 03-05-2021, 11:37   #6
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Re: Wiring both parallel and linear in one array...can I do so?

Thank you all for the advice. I believe I will purchase a second mttp and run a second line to batteries. Really appreciate the comments.
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